Building an ebike battery. Watts

DIY 48V electric bike battery pack with 18650 lithium battery.

18650 is the originator of lithium-ion batteries. a standard lithium-ion battery model set by Sony in Japan in order to save costs. 18 represents a diameter of 18mm, 65 represents a length of 65mm, and 0 represents a cylindrical battery

Noramlly 18650 batteries are divided into lithium-ion batteries and lithium iron phosphate batteries. The nominal voltage of the lithium ion battery is 3.7v, the charging cut-off voltage is 4.2v, the nominal voltage of the lithium iron phosphate battery is 3.2V, the charging cut-off voltage is 3.6v, the capacity is usually 1200mAh-3000mAh, and the common capacity is 2200mAh-2600mAh.

It is the same for lithium batteries marked 3.7V or 4.2V. It’s just that each manufacturer’s label is different. 3.7V refers to the platform voltage (typical voltage) when the battery is discharged during use, and 4.2V refers to the voltage when the battery is fully charged. Common rechargeable 18650 lithium batteries, the voltage is marked 3.6 or 3.7v, when fully charged is 4.2v, this has nothing to do with the power (capacity). The mainstream capacity of 18650 batteries ranges from 1800mAh to 2600mAh, (the capacity of 18650 power batteries is mostly 2200~3600mAh). It is generally believed that if the no-load voltage of the lithium battery is lower than 3.0V, it is considered to be exhausted (the specific value depends on the threshold value of the battery protection board, such as lower than 2.8V and 3.2V). Most lithium batteries cannot be discharged with no-load voltage below 3.2V, otherwise excessive discharge will damage the battery (generally, lithium batteries on the market are basically used with a protection board, so excessive discharge will lead to the protection board can not detect the battery, so that the battery can not be charged). 4.2V is the maximum limit voltage for battery charging. It is generally believed that the lithium battery is fully charged when the no-load voltage is charged to 4.2V. In the process of battery charging, the battery voltage gradually rises from 3.7V to 4.2V. Lithium battery charging cannot charge the no-load voltage above 4.2V, otherwise the battery will be damaged. This is the special feature of lithium batteries.

Prepare a spot welder, this is sequre SW1 spot welder

Make a nickel plate, which is used to connect the battery electrodes.

(Nickel sheets need to be cut in two lengths)

Use a special fixture to locate the battery and arrange the batteries

Weld the nickel sheet with the same electrode of the battery so that the batteries are connected in parallel. Only increase the capacity without increasing the voltage.

Every 7 in parallel, completely manual spot welding, this is the most space-saving arrangement.

Two two arranged in positive and negative directions. Use barley to directly insulate the battery row.

Each line of battery should be separated with highland barley paper to prevent skin damage resulting in short circuit. The voltage of the battery pack welded in series is multiplied by 13 times, 3.7v multiple by 13 is equal to 48.1v.

You can see the highland barley paper in the middle of two lines of battery.

Secure the entire battery pack with duct tape and use a heat-resistant one as much as possible.

Cover the top and bottom with highland barley paper and fix it, mainly for insulation.

Fix the battery management protection module.

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Cheap Li-ION ebike batteries

Cheap Li-ION ebike batteries cost less than a tenth of the price of brand name batteries of the same capacity. A common 36 volt, 10AH Li-ION battery pack sells for around US300 on Amazon where similar capacity batteries for brand name electric bikes are over 3000. Here’s the thing There is a trade off between quality and economy. Low cost replacement batteries are cheap for a reason. There are a number of issues with cheap ebike batteries: They are unreliable, frequently constructed incorrectly, rarely meet their claimed capacity rating, and are often dangerous. Despite the drawbacks, the relatively low cost of cheap batteries is compelling as brand name replacements are beyond the budget of most ebike owners. This raises the question:

Which batteries are best for ebikes?

For the past 20 years, the best ebike batteries have used Li-ion 18650 cells. Li-ion has dominated as the best technology and advancing chemistry continues to increase capacity and reliability. Li-ion provides the highest power for size. It is reliable, light and cost effective.

For the next few years, the electric vehicle world will continue to use Li-ion chemistry and Li-ion continues to be the best option for most electric bicycles.

If you want maximum power for your dollar then lead acid batteries are the best option. The issue with lead acid batteries is that they are over 4 times the weight of Li-ion equivalents. For electric bikes, the extra weight of lead acid batteries is a problem for most riders.

Many alternative battery chemistries have shown promise over the years. Lithium polymer (LiPo), Nickel metal hydride (NiMH), and Lithium Ferrous (LiFe) have all tried and failed to better Li-ion.

There is, however, massive investment in a range of new technologies which extend the range that electric vehicles can travel before requiring a recharge. The most promising technology that is beginning to emerge is rechargeable hydrogen cells. [click here to read our article on ebike batteries using hydrogen cell technology]

Rechargeable hydrogen cells are available now although they are in an early phase of production. In 2021, this very new form of powering electric bikes is beginning to roll out in Australia. Hydrogen cells for electric bikes would be expected to reach Europe and the US in 2022 if the technology proves to be successful.

As the roll out of cost effective hydrogen cells is new to the market, it is still too early to say whether they will begin a revolution in powering electric vehicles.

Ebike battery replacement

Once you have coughed up the substantial investment required to purchase your e bike, you typically have a year or two of good use before the battery supplied with the bike begins to fail. If you can afford a brand name ebike, you would typically expect the battery to last two to three years before the travel distance becomes annoyingly short.

It is a shock to most e-bike owners that replacement batteries for most ebikes can be more than half the price of a replacement bike with the latest battery fitted. In addition, the Rapid re-design of ebikes often means that it is difficult to obtain a replacement battery that fits your model bike.

When the battery dies, ebike owners are forced to seek a low cost replacement, or scrap the bike completely. The problem is that a good replacement battery by itself can cost as much as the e-bike with the battery included.

Why are cheap ebike batteries unreliable?

BMSs protect Li-ion battery packs from a range of potentially damaging issues. Batteries can be damaged if they are overcharged, drained excessively, discharged too quickly or if they overheat. BMSs ensure that the individual cells within the battery pack operate within their specified limits.

There are 2 types of BMS. The most important BMS is an overall management unit which manages all the individual cells within the battery pack. Each battery cell within the larger battery pack can also have individual protection circuits.

Battery cells with individual battery protection circuits can help to further protect each cell. They provide secondary protection if the main BMS is not providing sufficient protection for the cell.

Low cost batteries seldom use secondary protection within the cell as they are usually more costly and have a slight drain on the power of the cell. Ultimately, secondary protection within the individual battery cells is not necessary as the main BMS should provide good protection.

Low cost ebike battery packs use triple layer Printed Circuit Boards (PCBs) which are more prone to failure and cannot be cost-effectively repaired. Production line experts advise that triple layer PCBs have between 30-40% failure rate on leaving the assembly line due to warping effects.

Three layer PCBs offer a small cost saving over 4 layer technology but when price is of prime importance, reliability suffers.

China is the world’s largest manufacturer of cheap ebike batteries. Multiple layer PCB’s (4 layer or 2 layer) are more reliable but are difficult to source and are not produced in the same quantities in Chinese factories.

The greater complexity of 4 layer PCBs make them more expensive to design and produce. In addition, although 2 layer PCBs are usually cheaper, the circuit boards are larger and heavier than PCBs with more layers. As 2 layer BMS are not as popular in Chinese manufacture they are not in the same volume and, therefore, are more expensive.

In addition, the technology of poor quality PCBs can have an effect on the reliability of battery packs. Higher price PCBs can provide smarter cell maintenance to reduce the power supplied by the battery to better protect the individual cells in the battery pack from damage. Similarly, more expensive BMSs can protect individual cells from overcharging and overheating.

Picking The Type Of Battery

There’s quite a few types of battery that you could power your ebike with.

Some of the most common battery types include:

The names of these batteries come down to the chemistry used inside them. What makes them work is a combination of different chemicals. These interact to produce electricity! (Very simplistic view, but we don’t really need to know much more than that.)

So how do you decide what type of battery to use?

Here’s a quick rundown on each type and their uses.

Lead Acid

Lead acids batteries are known for being economical and robust for bulk applications. However they’re also known for being very heavy, and not as power dense as other battery chemistries. High power density means that for a specific weight and volume it has higher capacity. Low power density means the opposite. For the same size and weight battery, it has less capacity.

There’s 3 main uses for lead acid batteries.

They can be used for starter motors in cars. They’re also beneficial for stationary applications like power backup. Lastly lead acid batteries are great for deep-cycle applications (most often wheelchairs, scissor lifts, golf carts, house bus batteries and more).

Deep-cycle lead acids batteries are like these ones here!

Is this the best ebike battery?

We all know that more capacity is good in the ebike world, right? So we probably don’t want to use an overweight, clunky lead acid battery.

We’re not going to get very good range because we need to make our bike so heavy!


Nickel-Cadmium batteries are very rugged and forgiving. This allows for large cycle counts if maintained correctly.

They’re able to be ultra-fast charged without compromise, and have great load performance. Meaning they won’t sweat it if you punch the throttle!

Nickel-Cadmium is most often used in the airlines. Yet it has some drawbacks.

It has low power density. Has a memory effect so needs to be discharged (fully!) periodically. Plus it has a very high (shockingly in fact) self-discharge rate. Nickel-Cadmium batteries will self-discharge 20% over the first 24 hours after being charged.

Power tools can also use nickel-cadmium batteries like these Tenergy Batteries.

Is Nickel-Cadmium the best ebike battery chemistry?

All of these drawbacks make them not very good ebike batteries. But it still can be done if you were really determined!


Nickel-Metal-Hydride batteries can hold about 40% more charge than Nickel-Cadmium. They also have less of a memory effect so don’t need to be fully discharged as much.

However Nickel-Metal-Hydride batteries don’t have decent longevity. They’re also fickle to deal with when charging. Requiring a complex charge algorithm. Nobody wants to fluff around with that!

They generate heat quickly and have high self-discharge.


Ah, good old lithium ion batteries.

They’re in our smartphones, our laptops and our digital cameras. Pretty much everything we use in our day to day lives has a lithium ion battery.

There’s also many different kinds of lithium ion batteries.

In my own ebike battery, I have Samsung 25R 18650 cells. These have lithium manganese nickel chemistry.

Other popular cells are Panasonic GA 18650 cells. These are newer type batteries of LiNiCoAlO2 chemistry (Lithium Nickel Cobalt Aluminium Oxide). Also known as NCA cells.

Now these are the type of cells you want for the absolute best ebike battery!

A large battery that would be common for an ebike would be something like this 36V li-ion battery for your downtube. Alternatively you can get batteries that mount on a rear rack over your rear wheel!

What Do Volts And Amps Do?

Volts and amps are two very important parts of choosing an ebike battery. They can make or break your build (or set your bike on fire by accident too!)

First let’s start with volts.

What Do Volts Do To My Ride?

Every ebike motor designed will have been made with a specific input volt range.

This means that you cannot power your ebike with too little, or too many volts.

Too little volts means that you won’t have enough pep to give the motor. Too many volts will fry the sensitive electronic components inside the motor.

Most ebike motors will accept either 36 or 48 volts. These are the two most common nominal voltages.

That’s another important thing to know about ebike batteries. They’re most often measured by nominal voltage. Nominal voltage is just a fancy way of saying the average voltage. This is because each cell inside a battery can hold a specific range of volts.

Most Lithium-Ion batteries (Li-Ion) will have 18650 cells inside. Lithium Cobalt Oxide battery cells hold 4.2V when fully charged and 3.0V when discharged.

building, ebike, battery

My ebike battery has lithium manganese nickel cells, which we’ll FOCUS on here.

48V batteries generally have 13 cell clusters. Each cell cluster has a nominal voltage of 3.7V. So we can calculate 3.7V 13 cells = 48.1V or 48V nominal.

When fully charged however, this “48V” nominal battery will actually hold 4.2V 13 cells = 54.6V.

As you discharge the battery, it will drop each cell from 4.2V down to 3.0V – a minimum voltage of 3.0V 13 = 39V.

Volts translate into speed on your ebike. If you juice up your ride with more volts (but still within the operating limits of your motor!!) then you’ll reach a higher top speed. Assuming everything else stays constant.

I have a 52V battery from Luna-Mate (the New Zealand/Australia equivalent of Luna Cycle.)

Fresh off the charger I get 58.8V of jaw dropping power and speed!

Amp Up My Ride?

Amps are the measure of flow at a certain pressure (volts) right?

What this translates to in real life is torque! amps that your motor has available and can handle at once means more wheelie popping torque.

So my 52V 12.5Ah battery can peak at 70A and a continuous draw of 50A.

This is simply the rating of the battery. The motor might not pull that much current.

Motors only pull as much current as they need, so you won’t be able to kill a motor by selecting a battery with too high of a current output.

So if volts are the “oomph” into your ride, amps are how quickly the battery can deliver those volts. volts = more “oomph”. Higher amp rating means more “oomph” per second (or whichever time interval you want to use). So you get more power all at one time meaning more torque.

torque = more wheelies. 🙂

So What Is The Best Ebike Battery?

If you’re after a reliable, safe and proven ebike battery, lithium-ion is the only way to go.

As more and more people get ebikes and demand lithium-ion batteries, they’re going to become more affordable. At the moment a reputable battery will cost around 500USD.

If you want more capacity or more volts, you’ll be paying much more. If you want less capacity or volts, you can get some very economical batteries.

Even though they are currently the best ebike battery, lithium-ion may not stay that way forever! Which is why you’ll find information on battery updates here!

Lithium-ion batteries need to be cared for in a specific way. We’ll explore this in another post in extensive detail!

If you want to combine your newly picked battery with a kit for your mountain bike – check out this article here!

For now, just keep your eyes peeled for the best ebike battery deals you can. Stores such as Luna Cycle or EM3EV will have great batteries that are safe and reliable.

I hope you’re now more informed about your battery choices! There’s still plenty to learn, but we can learn it as we go.

Have fun and as always, feel free to reach out to me in the Комментарии и мнения владельцев or contact me here!

What should I take into account in the battery of an electric bike?

The e-bike battery package can be built according to the user’s needs using high-capacity cells or high discharge cells. The most common need is to maximize travel, meaning we usually put LG MJ1 18650 cellsto provide 3.5Ah capacity per sensor. Another excellent, slightly cooler option is the Panasonic-Sanyo NCR18650GA 18650 battery cell,3.5Ah capacity and 10A discharge.

The lithium battery possible bms is also the hardest element in the battery. The BMS charge control circuits from the manufacturer have pre-programmed in-control. It involves not only monitoring battery performance, but also discussion sup with the bike management system. For example, the battery tells information about its charge to the bike’s driving computer, which requires much more complex programming. Of course, e-bike manufacturers do not sell separately BMS circuits, but directly from new batteries.

BMS is the biggest challenge for the do-it-yourself construction. The battery pack may keep the battery dead if it has been empty for a long time. Even if the cells are loaded separately back into a good reserve, the programming of BMS cannot usually be changed at home. In this case, you will need to buy a new battery or put in a generic bulkkiBMS that monitors the battery cells, but does not know how to do anything else. Then the electric bike can run on an old battery, but it no longer knows the same tricks as the original.

Do-it-yourself e-bike battery

Only BMS status is an obstacle to those who are handy with their hands. If the BMS is very awake in the battery, but the battery cells are tired, the cells can be replaced.

Here’s a good example for english speakers in the video:

The video makes 13S2P, or 13 cells in series, 2 parallel battery packs. It uses Samsung INR18650-25R 18650 battery cellsthat provide 20A continuous discharge current and 2.5Ah capacity. The parallel connection of two cell lines means 5Ah capacity and 40A discharge current in the battery pack. 13 cells in a stick, i.e. when connected in series, make the battery pack 13x 3.6V = 46 V.

What does it take to get a battery?

When building the battery pack, the battery cells must be as close as possible to each other. In the worst case, if the battery has a high voltage difference, you can build a battery that has not worked.

Connecting the batteries into a battery pack is done by spot welding. Spot welding is practically the only working way, as knocking heats the battery too much and at worst spoils the entire cell.

Spot welding supplies electrical current to the welding site, which provides the heat required by the weld. The result is a very neat welding result and the battery cell remains intact.

For more information on how to design and build your battery, see Visit at least check out the images.

Custom-made e-bike battery

If your battery is running out of time, you can also send it to us. We’re analyzing the potential for that condition and re-encapitsion. After the measurements, we agreed with the customer which direction to go with the project. We can order any battery cell from the battery pack, including the new 20700 and 21700 battery cells.

The cost of work consists of battery cells and work done. Depending on the complexity of the battery, the work can cost 150-200 euros. As a result, we’ll send back a battery that probably has better features than original ones. (No need to use the most cheap cells, so you can maximize, for example, the capacity of the battery size within the limits allowed.)

The cells of the e-bike batteries depend a lot on the battery structure and desired features, so please contact us by email info @

At least the battery model and preferably a picture of the battery should be attached to the message. Let’s build the batteries that are right for you!

You can send the battery to:

  • Jesi Verkkokaupat Oy
  • Pääskynlento 13 B 43
  • 20610 Turku, Finland
  • 045 263 8565
  • Don’t forget to bring the charger!

What is a 18650 Battery?

A 18650 battery is a lithium-ion battery that can be recharged. The 18650 designation comes from the physical dimensions of the battery, which are 18 mm in diameter and 65 mm in length. The 0 represents the cylindrical shape of the battery.

18650 is one of the most common types of lithium-ion batteries. They are used in a wide variety of devices, including laptops, vapes, flashlights, and light electric vehicles.

Light electric vehicles such as e-bikes prefer 21700 and 18650 batteries.

How to Choose the Best 18650 Battery for Your E-bike

When choosing battery packs for your electric bike, you’ll want to consider the main factors:


The capacity of a battery is measured in milliampere-hours (mAh). The higher the mAh rating, the more energy the battery can store. A higher capacity lithium-ion rechargeable battery will give you a longer range on your bike. A higher capacity also means that the battery will take longer to charge.

Continuous Discharge Rating

The discharge rate of a 18650 battery for an e-bike is measured in terms of continuous current (C). A higher C rating means that the battery can provide more current for a longer period without being damaged.

building, ebike, battery

Higher Continuous discharge ratings are important if you’ll be using your bike for high-performance applications, such as racing or off-road riding.


It’s important to make sure that the 18650 lithium-ion batteries you choose are compatible with your bike’s controller.

Other factors that can guarantee you a good pack of li-ion for your e-bike include:

18650 e-bike cell manufacturers

Some 18650 battery brands are better than others in terms of quality and performance including continuous discharge rating.

There are many brands of 18650 batteries from reputable manufacturers, such as:

Panasonic 18650 lithium-ion batteries are among the most popular on the market. They are known for their high quality, good prices, and performance.

LG Chem 18650 is also very popular. They are known for their high energy density and long life.

Samsung SDI

Samsung 18650 is common in laptops and other devices. They are known for their high quality and reliability.

Sony 18650 is also common in laptops and other devices.

CATL is known for manufacturing high-quality 18650 lithium-ion. They are among the best batteries on the market with good prices.

BYD is a Chinese battery manufacturer. They are known for their good quality and competitive prices.

Toshiba 18650 li-ion are also common in laptops and other devices. They are known for their high expectancy and more power.

A123 Systems

A123 Systems is known for its high-quality 18650 li-ion. They are used in a wide variety of applications, including electric vehicles, digital cameras, and vaping devices amongst other devices.

18650 battery chemistry

The chemical composition of 18650 batteries is very important in choosing a rechargeable battery. The chemical composition includes:

Each of these chemistries has its advantages and disadvantages.

building, ebike, battery

Lithium iron phosphate (FePO4) is the most stable of the four chemistries. It has a very low rate of self-discharge and is not susceptible to thermal runaway. However, LiFePO4 has a lower energy density than the other chemistries.

Lithium nickel cobalt aluminum oxide (NCA) lithium battery comes with a high power density and good stability. It is one of the most popular battery types on the market. It is quite affordable with a low continuous discharge rating.

Lithium nickel cobalt magnesium oxide (NCM) batteries are the most popular type of lithium battery on the market. They are affordable, have a long cycle of life, and are very stable. NCM is available in a variety of voltages, ranging from 3.6 volts to 4.2 volts.

The 18650 e-bike battery voltage

18650 batteries come in a variety of voltages. Your choice of 18650 e-bike battery voltage will ultimately depend on the voltage of your bike.

The e-bike battery voltage you choose will also affect the amount of power your bike has. A higher voltage battery will give your bike more power, while a lower voltage battery will give your bike less power.

Features of the 18650 battery packs for e-bike

Some 18650 batteries come with built-in protection circuits Multi-function Protective Circuit Board (PCM). PCM is used to protect the cells from overcharging, over-discharging, overcurrent, and short circuits.

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